Gun control proponent Gabby Giffords and her husband Mark Kelly have chosen to endorse Democrat presidential hopeful Hillary Clinton over Bernie Sanders because of Clinton’s stronger gun control stance.

Clinton supports expanding background checks to cover all sales; this includes closing the non-existent gun show loophole and online sales loophole. Clinton also proposes expanding “instant” background checks to an indefinite time frame and adding the no-fly list to background checks.

Clinton especially differentiates herself from Sanders by seeking to open up gun stores and gun manufacturers to lawsuits from victims of gun crime.

These distinctions have garnered Clinton the Giffords-Kelly endorsement.

CBS News reports that Giffords “has been a staunch advocate of tightening firearm legislation since 2011, when a gunman opened fire at a supermarket parking lot in Tucson, shooting Giffords in the head and killing six others.” Giffords and her husband emerged from that attack determined to require every would-be gun owner to pass the same background check Giffords’ attacker passed to acquire the gun with which he shot her.